<DOCUMENT>
<TYPE>EX-24
<SEQUENCE>2
<FILENAME>paulrubinpoa3.txt
<DESCRIPTION>EDGAR SUPPORTING DOCUMENT
<TEXT>
POWER OF ATTORNEY
Know all by these presents, that the undersigned hereby constitutes
and appoints each of John Varian, Fred Kurland, Russell Wood and
Diane Wilcock, signing singly, his true and lawful attorneys-in-fact to:
(1)execute for and on behalf of the undersigned Forms 3, 4 or 5 in
accordance with Section 16 of the Securities Exchange Act of 1934, as amended
and the rules and regulations promulgated thereunder (the "Exchange Act");
(2)do and perform any and all acts for and on behalf of the undersigned which
may be necessary or desirable to complete the execution and delivery of any
such Form 3, 4 or 5 and timely filing of any such form with the United States
Securities and Exchange Commission and any other authority; and
(3)take any other action of any type whatsoever in connection with the
foregoing which in the opinion of such attorney-in-fact, may be of benefit
to, in the best interest of, or legally required of, the undersigned, it being
understood that the documents executed by such attorney-in-fact on behalf of
the undersigned pursuant to this Power of Attorney shall be in such form and
shall contain such terms and conditions as such attorney-in-fact may
approve in his discretion.
The undersigned hereby grants to each attorney-in-fact full power and authority
to do and perform all and every act and thing whatsoever requisite,
necessary and proper to be done in the exercise of any of the rights and
powers herein granted, as fully to all intents and purposes as such
undersigned person might or could do if personally present with full power of
substitution or revocation, hereby ratifying and confirming all that such
attorney-in-fact, or his substitute or substitutes, shall lawfully do or cause
to be done by virtue of this power of attorney and the rights and
powers herein granted.  The undersigned acknowledges that the
foregoing attorneys-in-fact, in serving in such capacity at the
request of the undersigned, are not assuming any of the
undersigned's responsibilities to comply with
Section 16 of the Exchange Act.
This Power of Attorney shall expire on August 31, 2016.
IN WITNESS WHEREOF, the undersigned has caused this
Power of Attorney to be executed and it shall be effective
as of August 31, 2014.
/s/ Paul D. Rubin
Paul D. Rubin, M.D.
</TEXT>
</DOCUMENT>
